<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8" />
    <title>Title</title>
</head>
<body>
    <div>
        <ul>
            <li id="l1" class="c1">北京</li>
            <li id="l2">上海</li>
            <li id="c3">西安</li>
            <li id="c4">深圳</li>
        </ul>
    </div>
</body>
</html>